The embodiments of the present invention relate to gas generating systems used to provide gases for gas-actuatable devices incorporated into, for example, a vehicle occupant protection system.
Gas generating systems may be provided with multiple chambers to allow the amount of inflation gas produced to be adjusted based on need. For example, a primary chamber may be activated or deployed based on an estimated need for a relatively smaller quantity of gas. An additional, optional secondary chamber may be independently activated or deployed based on an estimated need for a relatively greater quantity of gas. The secondary chamber may contain a gas generant material therein and may be activated after activation of the first chamber and release of at least a portion of the gas generated in the first chamber. After activation, the secondary chamber generates gas and may release the gas into the primary chamber through openings connecting the two chambers. The gas from the secondary chamber then exits the primary chamber into an associated gas-actuatable device.
In a situation where the secondary chamber is in fluid communication with the primary chamber during combustion of the secondary chamber gas generant material, the pressure within the secondary chamber may fall below a value conducive to efficient combustion of the material and/or below a value conducive to minimizing the generation of undesirable effluents, due to leakage of gases through the openings.
Therefore, a need exists for improved methods and/or mechanisms for controlling pressure within a secondary chamber in fluid communication with the first chamber, during combustion of a gas generant positioned within the second chamber.